JUSTIN Timberlake brought two dates to celebrate his third stint as host of “Saturday Night Live.” At the show’s after-party at Primehouse, the singer stayed till 4 a.m. with his girlfriend, Jessica Biel, as well as his father, Randy Timberlake. “His dad seemed really proud of him,” says a spy. Also there were Blake Lively and Penn Badgley, “Star Trek” stars Zachary Quinto and Chris Pine and Patricia Clarkson and Police Commissioner Ray Kelly, who sat at executive producer Lorne Michaels’ table.